Free-wheeling clutches comprise internally controlled coupling means for coupling between a pair of co-axial shafts. Usually a number of sets of reversible locking mechanisms are replicated in a circumferential array. A one-way clutch should allow free relative movement (free-wheeling) of a first component in relation to a second component when the relative motion between the components is in a first direction (for example, a positive direction), but should not allow the relative motion to become negative. The clutch should lock the two components as soon as the relative motion tends to become negative. A one-way clutch can be regarded as a mechanical equivalent to an electrical diode—a device for transmitting power in only one direction.
Free-wheeling or one-way clutches are used in many mechanical engineering applications. For example, bicycle chain drives have a ratchet-based one-way clutch which prevents the chain and cranks being turned by the wheel when the rider is coasting. They are used in automatic transmissions in land vehicles. They are used in machines for making electric energy in a dynamo driven by reciprocating motion, such as to-and-fro wave motion.
Existing one-way clutches rely on various locking mechanisms to reversibly lock the first and second shafts. One class of locking mechanism is of the ratchet type, with one or more spring-loaded pawls (also called struts) on a first assembly reversibly engaging with a corresponding number of pockets on a second, apposed assembly. Unless counteractive steps are taken, this class produces a clicking noise during freewheeling and exhibits backlash, but when engaged the pawls provide an effective direct coupling of torque without undue stress to materials. Another class involves a wedging action between either a strut, sprag, ball, or roller which enters and becomes jammed within a tapered recess when engaged. Usually a number of sets of locking mechanisms are replicated in a circumferential array. While these one-way clutches are relatively noiseless and have little backlash, the wedging action inherently focuses a significant strain on a small surface area where the strut, sprag, ball, or roller makes contact, amplified by the tangent of the taper and by excessive torque. The wedging action (after a little backlash) significantly magnifies the force applied per unit area It is likely that the material will show permanent distortion at the surface and this type of one-way clutch typically has a short life.
Reverting to ratchet types, there is a particular class of radially oriented, planar one-way clutches employing spring-loaded pawls (struts) to reversibly connect between the parts. Existing one-way clutches of this type exhibit a certain amount of reverse motion (also known as backlash) before the parts turn into a co-engagement position and become locked together. By the time positive engagement occurs some momentum may build up and the impulse occurring at the time of contact may be harmful. It may shock the materials to such an extent that fatigue occurs (if only after a number of cycles), hence the clutch parts must be made strong enough to resist failure. In the case of power-generating machines including one-way clutches, the backlash motion may cause considerable forces that may affect many components of the transmission.
Vibration or noise are other likely problems. If resilient members are used to buffer the impacts, unexpected resonances may occur and the resilient material will fail in time.
No prior art is known in relation to Example A or to Example C (as detailed below). In relation to Example B, prior-art biasing means lacking directional sensing are widely known; most are springs. Ruth (U.S. Pat. No. 6,116,394), provides a running-rail solution to the noise problem.